Ceiling structures, such as suspended ceilings, are typically made with an interlocking grid of struts or tees, suspended from the concrete slab of the roof or the floor of the next storey of the building and having panels of acoustic or similar material supported on such struts.
Ceiling structures may also be of gypsum wallboard, plasterboard, plaster or the like and this invention is equally applicable to the thermal protection of fixtures in such other ceiling types.
Principally, this invention is concerned with ceilings which are located in multi-storey public and commercial buildings but the invention is broadly applicable to any type of building or ceiling structure where services are provided in the space or void between the ceiling and the concrete slab, roof or other structure disposed above such a ceiling.
Such ceilings incorporate various fixtures such as lighting troffers, air-handling diffusers and grilles, and, in some cases, loudspeakers for music or public address systems.
Building codes customarily require that such a composite ceiling structure have a predetermined fire rating; the ceiling must remain intact and protect the so-called void, i.e. the space between the ceiling and the overlying slab or roof, from excessive heat for a certain period of time in the event of fire below the ceiling.
Usually, the acoustic panels or other ceiling materials themselves are fireproof and are highly resistant to the transmission of heat so that they constitute adequate thermal protection for the ceiling void.
However, where there are openings through the ceiling for the various fixtures installed therein, the ceiling void may be virtually unprotected. The ceiling fixtures are usually made of relatively thin sheet metal and such metal will, of course, transmit heat from a fire quite rapidly into the ceiling void.
For these reasons, building codes require that the ceiling fixtures themselves be provided with some form of barrier, enclosure or shield of fireproof or heat-proof material over the fixture.
In the great majority of cases, such shields are presently fabricated from relatively rigid fireproof materials such as gypsum wallboard, ceiling tile or the like by cutting such material generally into rectangular pieces which are then roughly assembled in place in the form of a box over the lighting or other ceiling fixture. Such known shields are often loosely fastened together with nails.
The custom fabrication of such fireproof enclosures on a building site is wasteful of labour and unreliable. Additionally, it causes confusion as to the division of responsibility between the various trades.
In addition, materials such as gypsum wallboard are relatively fragile and are not, therefore, easily formed or fabricated into such rectangular box-like enclosures. In many cases, the effectiveness of the fire protection provided by such enclosures is drastically reduced after a period of time since they often have a relatively flimsy insecure construction and may fall apart or become seriously damaged, for example, when maintenance work is being carried out in the ceiling void. Frequently, such damaged boxes cannot be repaired or the repair effected by a tradesman might be totally inadequate.
While other forms of heat-resistant material and thermal insulation are available, they are in very many cases possessed of similar inherent disadvantages when considered for this purpose. Ceiling fixtures come in so many different shapes and sizes that the prefabrication of specially shaped shields or enclosures for such a variety of fixtures would be too costly and impractical.
For all these reasons, it is, therefore, highly desirable to provide a thermal shield for use over a ceiling fixture so as to provide thermal protection and which shield is simple and inexpensive to manufacture, simple and effective in use and not easily damaged or destroyed in use and particularly during servicing of the ceiling fixture. Additionally, such a shield should remain effective for its intended purpose throughout the useful life of the ceiling structure itself. It is also desirable to provide a thermal barrier material which will be readily adaptable to a variety of different uses and which may be cut, shaped, fastened, etc., to fabricate such a thermal shield, without special tools or fasteners, other than those normally available on a building site.
One important object of this invention is, therefore, to provide a novel thermal barrier material for the fabrication of thermal shields and which material presents the aforementioned characteristics.
Yet another object of this invention is to provide a thermal shield or fire barrier for disposition over a fixture in a ceiling structure for the purpose of reducing the transmission of heat upwardly through such a fixture.
A further object of this invention is to provide a thermal shield or fire barrier for the aforesaid purpose and which shield presents one or more of the desired characteristics as hereinbefore identified for such a shield.
Other objects of the invention will become apparent as the description herein proceeds.